It's really impressive you made this in the time constraints without using a game engine!
It looks nice considering everything is just a rectangle and the player's health being how bright they are is pretty intuitive. The patterns of the obstacles can get pretty mesmerizing, in a good way.
To be honest I found it was much easier to hold down space and remain as a small cube in the center of the screen than to use the advantage of the larger cube's speed at any point. Perhaps if there were 'walls' of obstacles at times which took up large chunks of the screen it would force the player to rush to one area, rather than always being able to weave in between singular blocks. (Well, maybe that does happen later? But I survived for what felt like a fairly long time.)